But, as expected, it didn’t take long for various interest groups that feel stung by the measure to make their views known, and that will likely make the lawmakers’ unity fleeting.

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Even before the legislation was formally unveiled, one of the most powerful groups in conservative circles, Americans for Prosperity, warned that plans to slap a tax on imports from U.S. companies that move jobs abroad “has the potential to derail much-needed reform.”

That was followed by denunciations from the influential National Federation of Independent Business, a small business lobby; the National Association of Home Builders; Independent Sector, which represents charities; the National Farmers Union; and even the American Institute of Architects.

That will give lawmakers plenty to think about as they brace for lobbyists to descend on their offices to fight for and against parts of the bill that will affect their profits, charitable donations and public services.

But Thursday appeared to be all about rallying around what could be the only major legislative accomplishment Republicans have to take into the 2018 midterm elections.

Rep. Mark Walker (R-N.C.), chairman of the Republican Study Committee, said he didn’t hear enough concerns among members of his party when they were briefed on the plan to slow its momentum.

“I don’t think anyone voiced anything that was just overwhelmingly a shutdown concern, to my surprise,” Walker said. “Guys from different caucuses, from different groups, were all speaking in favor of it. Not everybody’s happy about everything but … I was actually a little taken aback at how much unity there was in the room at the overall package.”

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Rep. Mark Meadows (R-N.C.), head of the often balky Freedom Caucus, said he had some concerns about proposed changes to housing tax breaks and also with how the bill treats small businesses, but said he’s nevertheless “leaning yes” on the plan.

“I believe we’ll get there, and I’ll be optimistic that the few remaining issues will get addressed,” he said.

Lawmakers from high-tax states continued to grumble that the proposal would eliminate a deduction for state and local income and sales taxes, while keeping a property tax write-off that would be capped at $10,000.

“The property tax is still too low,” Rep. Tom MacArthur (R-N.J.) told reporters, adding that he’s already made a personal plea to House Ways and Means Chairman Kevin Brady (R-Texas). “I’ve done the math for my own state, my own district, and I’ve given the chairman of Ways and Means what I think the number needs to be.”

The unveiling of the 429-page bill — and a summary that runs 82 pages — kicks off what is sure to be a grueling slog to get legislation to President Donald Trump by the end of the year. The Senate is expected to follow up with its own plan as early as next week.

The bill would benefit a big slice of the American economy, with deep cuts in corporate tax rates, changes designed to make taxes on U.S. multinationals more competitive and tax cuts for individuals that Republicans say will significantly lighten their tax burden.

But it also includes provisions sure to stoke controversy and fierce lobbying, including new limits on the popular mortgage interest deduction. People could only deduct interest on the first $500,000 of loans for newly purchased homes, down from the current $1 million, and lawmakers would eliminate the break for second homes. The bill would also make it harder for people to sell their homes without paying taxes on any capital gains.

Experts warned that some middle-income people could see tax increases under the plan.

While big companies would get a significantly lower 20 percent corporate rate, down from 35 percent, they would face new limits on their ability to deduct interest on their loans, a new global minimum tax on their overseas earnings, and new taxes on U.S. companies heading abroad.

Republicans dropped a contentious plan to curb tax benefits for 401(k) retirement plans, which had GOP lawmakers cheering Brady at a closed door briefing on the plan.

Exactly who would win and lose in the proposal — dubbed the "Tax Cuts and Jobs Act" — has been a closely guarded secret, and many lawmakers will surely be surprised at the scope of changes needed to make the numbers behind the plan work.

The NFIB announced its opposition, citing restrictions lawmakers included on which small businesses can claim their lower tax rate on unincorporated "pass-through" firms. The issue has been one of the most difficult for lawmakers to work out, and could prove to be one of the most contentious going forward.

Though lawmakers would reduce the rate on those businesses to 25 percent, there would be limits on which firms could take advantage, provisions designed to avoid gaming by wealthy individuals.

Under the proposal, pass-throughs would get the lower rate on 30 percent of their profits, with the remainder taxed at ordinary income tax rates, though there would be circumstances in which businesses could qualify for a bigger share being subject to the special rate. That means, though, that some pass-throughs would actually pay more than 25 percent under the plan.

“This bill leaves too many small businesses behind,” said Juanita Duggan, the group’s president. “We believe that tax reform should provide substantial relief to all small businesses.”

The National Association of Home Builders said the legislation “eviscerates” housing tax benefits, and “abandons middle class taxpayers.”

The National Association of Realtors meanwhile has already begun lobbying against the proposal, running online ads in tax writers’ districts. “Don’t let tax reform become a tax increase for middle-class homeowners,” the ad says.

Independent Sector worries charities would suffer because the bill’s expansion of the standard deduction means far fewer people would take an itemized deduction for charitable giving. “The bill moves in the wrong direction,” said Daniel Cardinali, the group’s president.

Other business groups embraced the plan, including the U.S. Chamber of Commerce and the Business Roundtable.

"This bold tax reform bill is exactly what our nation needs to get our economy growing faster,” said Neil Bradley, a senior vice president at the Chamber of Commerce. Said Jamie Dimon, head of JP Morgan Chase & Co. and the Business Roundtable: "We support this tax reform effort because it is good for all Americans."

House Speaker Paul Ryan and his leadership team want to stay ahead of lobbyists and constituencies that they know will be at their door. They plan to create an interactive presentation for each member to show the bill’s economic impact on their district, and what different adjustments would do.

“The substantive issue is how all these changes add up for families in my district or other members’ districts,” said Rep. Patrick McHenry (R-N.C.), the Republican chief deputy whip. “And once people can see that then that will determine their level of support.”

The plan is Republicans’ top priority ahead of next year’s elections, and lawmakers are desperate for a victory to take to voters after the failed campaign to repeal the Affordable Care Act.

Republicans are hoping to move it quickly through the House, with committee action penciled in for next week. Lawmakers aim to forward it on to the Senate later this month. Senate Republicans are working on their own competing plan they aim to unveil next week. Lawmakers hope to land a compromise on Trump’s desk by the end of the year.

House leaders, who have written the plan in secret, had avoided identifying most of the breaks that would be quashed under the proposal in order to keep lobbyists at bay. But many Republicans had little inkling of what’s in the bill, and the strategy means leaders have not had much opportunity to build support among rank-and-file members for controversial proposals that will surely get more attention in the coming days.

The bill is loaded with sure-to-be contentious ideas affecting broad swathes of the economy. It would delete a long-standing deduction for people with high medical bills — including those with chronic conditions. People would have to live longer in their homes, under the bill, to qualify for tax-free treatment of capital gains when they sell their houses.

It would also kill long-standing breaks for adoptions, and for student loan interest costs. Private universities would face a new 1.4 percent tax on their investment earnings from their endowments. The Work Opportunity Credit, which encourages businesses to hire veterans, would be eliminated. So too would the New Markets Tax credit, which encourages investment in poor areas.

Tax benefits related to fringe benefits would be curtailed. It would also dump a long-standing break for casualty losses that allow people to deduct things lost in fires and storms, although it would continue to allow the provision for people hit by hurricanes — no doubt reflecting the influence of Brady, whose Houston-area district was hit by Hurricane Harvey.

Foreign companies operating in the United States would face higher taxes under the proposal, as would companies such as pharmaceutical firms that move overseas and want to sell goods back to the United States.

The bill would cut taxes over the next decade by $1.487 trillion, according to the official Joint Committee on Taxation. The estimate also shows the bill would likely run afoul of the Senate’s “Byrd rule,” named after the late Sen. Robert Byrd (D-W.Va.), which bars provisions adding to the government’s long-term debt.

For individuals, the plan would reduce the number of tax brackets to four from the current seven, with the top rate remaining at 39.6 percent. Republicans would more than double the income threshold at which the top rate would kick in to $1 million for married couples. They would simultaneously raise taxes on the rich, though, by limiting their ability to take advantage of their lowest income tax bracket. The 35 percent bracket would begin at $260,000 for married couples, and the threshold for a 25 percent bracket would be $90,000 under the plan .

Republicans would also get rid of personal exemptions, which are designed to adjust tax burdens for family size. The plan would instead double the standard deduction while increasing both the size of the child tax credit to $1,600, from the current $1000, while increasing the income threshold at which it could be claimed. They would also create a new $300 credit for adult dependents as well as another $300 “family flexibility” credit.

The bill would ease the estate tax by doubling the threshold at which it would kick in before eventually repealing it.

Aside from the lower corporate tax rate, businesses would also get the ability to immediately write off their investment expenses for the next five years. They would get a one-time reduced rate of 12 percent on their overseas earnings on liquid assets and a 5 percent rate on illiquid assets like overseas factories.

But they would face new limits on their ability to deduct interest payments on the money they borrow. They would also face a new 10 percent foreign minimum tax targeting companies that squirrel away money in offshore tax havens. Life insurance companies would lose a number of tax benefits, private activity bonds would be eliminated and tax-exempt bonds could no longer be used to help build professional sports stadiums.

Colin Wilhelm,Rachael Bade and Sarah Ferris contributed to this report.